Handle image sizing

[jonathanstegall]

I've tried to do this as part of migration, but it's unclear if this is correct.

• https://github.com/MinnPost/migrate-drupal-to-wordpress/commit/371837f7554201e194c9820b891f0bf04123dd9d
• https://github.com/MinnPost/migrate-drupal-to-wordpress/commit/0aadbd682c0a52ffb994925ecdaf1789ba77212d
• https://github.com/MinnPost/migrate-drupal-to-wordpress/commit/6a3e63dcdae1bf7fa59a2c25c8c712e8aec9c112

This is probably not all the relevant commits for this. There is also some functionality that sets the image sizes: https://github.com/MinnPost/migrate-drupal-to-wordpress/blob/master/migrate.sql#L1562-L1595

[jonathanstegall]

I think this has all been fine for a while now.